(1) Field of the Invention
The present invention relates to compositions comprising a herbicide, or combinations of herbicides, with or without a safener, and a repellent adjuvant, wherein the repellent adjuvant modifies the surface properties of the composition so that retention of the composition on foliage of the cultivated plant is reduced. In particular, the herbicide composition comprises a repellent adjuvant that is an aqueous solution of an an alkyltrialkoxysilane such as methyltrimethoxysilane and a water soluble silane coupling agent such as N-(2-aminoethyl)-3-aminopropyltrimethoxysilane or an aqueous solution of an organosiliconate such as sodium methyl siliconate.
(2) Description of Related Art
Many herbicides will cause injury to certain crop plants when applied in amounts that are effective in controlling weed growth. The damage to crop plants can be particularly severe when the crop plant is in an early stage of development, which is precisely the time when control of weed growth is most important. For this reason many herbicides are unsuitable for controlling weeds when crop plants are at particular stages of growth. Therefore, the inability to control weed growth results in lower crop yield and reduced crop quality because the weeds compete with the crop plant for nutrients, light and water. In an attempt to broaden the usefulness of various herbicides, various herbicide compositions have been developed which contain compounds known as “safeners”, also referred to as “antidotes”, “protectants” or “antagonists.”
The concept of using safeners to enhance the tolerance of crops to herbicides was developed in the late 1940's and has led to the development of particular herbicidal compositions that have the ability to control weed growth but without adversely affecting the growth or yield of a particular crop plant. However, the identification of an antidote which safens a particular class of herbicide or mixture of herbicides is not a theoretical determination but must be determined empirically. This determination is performed by observing the complex interaction of many biological and chemical factors, including the type of herbicide, the weed species to be controlled, the crop plant to be protected from weed competition and herbicidal injury, the developmental stage of the crop plant, and the safening compound itself. Moreover, the safener and herbicide must possess physico-chemical properties which allow an environmentally acceptable and stable product to be prepared. Therefore, because the discovery of herbicide/safener compositions is so empirically based, the development of effective herbicide/safener combinations is an expensive and unpredictable undertaking.
Isoxaflutole, an isoxazole herbicide, is a new soil-applied herbicide for use in corn. Researchers have reported that isoxaflutole provides excellent preemergence control of several broadleaf and annual grass weed species at rates ranging from 53 g/ha to 158 g/ha in conventional tillage and no-tillage corn (Bhowmik and Prostak, Weed Sci. Soc. Am. Abstr. 36: 13 (1996); Curvey and Kapusta, North Central Weed Sci. Soc. 51: 57-58 (1996); Geier and Stahlman, North Central Weed Sci. Soc. 52: 81 (1997); Luscombe et al., Proc. North Central Weed Sci. Soc. 59: 57-58(1994); Mosier et al., Proc. North Central Weed Sci. Soc. 50: 74 (1995); Obermeier et al., Proc. North Central Weed Sci. Soc. 50: 25 (1995); Simkins et al., Proc. North central Weed Sci. Soc. 50: 25 (1995); Veilleux et al., North central Weed Sci. Soc. 50: 75 (1995); Vrabel et al., Proc. North Central Weed Sci. Soc. 24-25 (1995); Wrucke et al., Proc. North Central Weed Sci. Soc. 52: 17(1997); and Young et al., Weed Sci. Soc. Am. Abstr. 38: 8 (1998)). The mode of action of isoxaflutole is the competitive inhibition of the 4-hydroxyphenylpyruvate dioxygenase enzyme (EC 1.13.11.27) (Pallett et al., Pestic. Biochem. Physiol. 62: 113-124 (1998); Viviani et al., Pestic. Biochem. Physiol. 62: 125-134 (1998)). Inhibition of this enzyme disrupts carotenoid biosynthesis causing a bleaching symptomology in susceptible species similar to herbicides that disrupt carotenoid biosynthesis by targeting the phytoene desaturase enzyme (Luscombe and Pallet, Pestic. Outlook, 29-32 (1996); and Pallett et al., Pestic. Sci. 50: 83-84 (1997)). While isoxaflutole has been shown to be an effective herbicide for controlling weeds, isoxaflutole also has been shown to cause injury to corn and other crop plants, especially when applied postemergent. For an example, see U.S. Pat. No. 5,627,131 to Shribbs et al.
Therefore, there is a need for a method for applying a herbicide post-emergence to a wide variety of cultivated plants that does not depend on the identity of the herbicide or the use of a safener. Such a composition would not be injurious to the cultivated plant but would maintain its ability to control weeds. The present invention provides compositions and methods for their use that satisfy this need.